1. Technical Field of the Invention
The present invention relates generally to the field of imaging systems. More particularly, the invention relates to an imaging system and method for achieving a large depth of field without decreasing the relative aperture of an imaging lens.
2. Background of Invention
A large depth of field is important in imaging systems having an imaging lens position that is fixed with respect to an image receiving surface, but in which the distance along the optical axis from the lens to the object to be imaged may vary significantly. In a typical imaging system, depth of field is inversely proportional to the relative aperture of the imaging lens such that the relative aperture of the lens must be decreased in order to increase the depth of field. Decreasing the relative aperture, however, reduces light sensitivity and resolution; and, as a result, it is difficult to design an imaging system that has a large depth of field while maintaining high light sensitivity and fine resolution.
There is, accordingly, a need for an imaging system that achieves a large depth of field without decreasing the relative aperture of an imaging lens.